Various types of defects exist on surfaces of a silicon-carbide wafer and an epitaxial wafer. Such defects increase a surface roughness of the silicon-carbide wafer, causing a bad influence upon the subsequent processes. A surface defect on the silicon-carbide wafer results in another defect in growing a single crystal layer and causes a rough surface. The surface defect on the epitaxial wafer may cause a partial isolation in laminating several layers. Further, when a device is fabricated using such a wafer, a leakage current may be increased by non-uniformity of metal electrode deposition and patterns.
For this reason, the life span of a device may be reduced and reliability of the device may be lowered. Thus, it is very important in manufacturing a high quality device to remove and control such a defect.
According to the related art, in order to control the surface defect of the silicon carbide wafer, halogen gas treatment is performed or hydrocarbon gas and hydrogen gas are applied so that the defects are controlled. An etching step may be generally performed through a wet etching scheme or a dry etching scheme.
For example, according to in-situ hydrogen etching, hydrogen is adsorbed on the surface of the silicon carbide wafer to reduce the surface energy, so that Si and C adsorbed on the surface of the silicon carbide wafer are smoothly moved. However, if the hydrogen acts as the etching cause of C, the stoichiometrical relationship on the surface of the wafer is broken, thereby causing the defects to the surface of the wafer.
In addition, the etching scheme based on hydrochloric acid (HCl) is used in the Si-face epitaxial growing, and prevents silicon (Si) from being aggregated on the surface of the wafer to reduce Si droplets and the surface defects of the wafer. However, if the etching for silicon (Si) is excessively performed, the etch-pit may be created to cause defects.
In addition, if the treatment of CHx is performed, carbon-bonds are induced on the Si-face surface to help grow the epitaxial layer representing less defects as compared with silicon (Si) representing a higher aggregation characteristic. However, if the treatment of CHx is excessively performed, a C—C bond may be crated to cause a problem in the bonding between the epitaxial layer and the silicon carbide wafer.
Therefore, a wafer and an epitaxial wafer having an epitaxial layer grown on the wafer, which represent a lower defect density by removing defect causes resulting from the excessive etching during the etching process, are required.
In particular, as shown in FIG. 1, when the wafer is etched by using HCl, silicon (Si) are excessively extracted due to the excessive etching of HCl, so that another surface defects may be caused after the etching process has been performed.
Therefore, in order to remove the surface defects resulting from the etching, a scheme of complementing silicon (Si) according to the excessive extraction of the silicon (Si) is required.